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SubjectRe: [RFC][PATCH] Disable CLONE_PARENT for init
| This won't fix the problem. The child won't autoreap itself if ->exit_signal
| != SIGCHLD.
|
| > If you want to make this change because of container-init issues, I think
| > you should just say so independent of this global-init case.
|
| Yes, agreed, the comment looks confusing.
|
| Oleg

Here is an updated patch with comments fixed.

Roland pls ack again if this is better.

---

Disable CLONE_PARENT for init.

When global or container-init processes use CLONE_PARENT, they create a
multi-rooted process tree. Besides if the siblings of init exit, the
SIGCHLD is not sent to init process resulting in the zombies sticking
around indefinitely.

Changelog[v3]:
- [Roland, Oleg] Simplify comment describing the change
Changelog[v2]:
- Simplify patch description based on comments from Eric Biederman
and Oleg Nesterov.
- [Oleg Nesterov] Use SIGNAL_UNKILLABLE instead of is_global_init()

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
---
kernel/fork.c | 8 ++++++++
1 file changed, 8 insertions(+)

Index: linux-mmotm/kernel/fork.c
===================================================================
--- linux-mmotm.orig/kernel/fork.c 2009-06-30 23:01:06.000000000 -0700
+++ linux-mmotm/kernel/fork.c 2009-07-01 14:43:10.000000000 -0700
@@ -974,6 +974,14 @@ static struct task_struct *copy_process(
if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
return ERR_PTR(-EINVAL);

+ /*
+ * To avoid multi-rooted process-trees prevent global and container
+ * inits from creating siblings.
+ */
+ if ((clone_flags & CLONE_PARENT) &&
+ current->signal->flags & SIGNAL_UNKILLABLE)
+ return ERR_PTR(-EINVAL);
+
retval = security_task_create(clone_flags);
if (retval)
goto fork_out;

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